Synthetic polyamides possessing antibacterial activity



United States Patent 3,345,341 SYNTHETIC PQLYAMIDES POSSESSING ANTIBACTERIAL ACTIVITY William Rhett Berry, Asheville, N.C., and Nathaniel Grier, Englewood, Ni, assignors to The American Erika Corporation, Erika, N.C., a corporation of Delaware No Drawing. Filed Sept. 5, 1963, Ser. No. 306,704 9 Claims. (Cl. 260--78) ABSTRACT OF THE DISCLOSURE Synthetic high polymer yarns possessing antibacterial activity are produced by incorporating in a liquid synthetic linear high polymer melt a small amount of a metal salt of pentachlorophenate or certain pentachlorophenyl esters and the melt is extruded through fine orifices to produce the yarn.

will retain their antibacterial activity despite scouring,

dyeing and repeated washing or laundering operations. The term yarn as used herein is intended to mean strand material such as threads, filaments, and fibers. The invention is primarily concerned with the production of fine denier, pliable yarns for use in hosiery fabrics, wearing apparel, sterile dressings, carpets, etc., that have the ability to inhibit and in certain cases destroy harmful or undesirable microorganisms that have come in contact with the fabric and yarn surfaces.

For many years it has been known that various compounds useful as bactericides or bacteriostats could be applied with a finish to the surface of fibers and fabrics which would render the fibers and fabrics resistant to bacteria on contact. Examples of this method of treating fibers and fabrics are disclosed in US. Patents No. 2,830,011 and No. 2,837,462. In general, fabrics or fibers treated in this manner are not satisfactory due to the short period of time the materials retain their antibacterial ac tivity which is at most only temporary. One or two washings severely diminishes or completely destroys the effectiveness of the fabric for inhibiting the growth of microorganisms.

In an attempt to correct these deficiencies, it has been proposed that antibacterial agents be incorporated directly into the polymer prior to the processing thereof into filaments or other articles. Of specific interest in this connection is US. Patent No. 3,034,957 which discloses the addition of bactericidal and bacteriostatic compounds to certain resins prior to molding or extrusion into fibers.

While the use of these agents was partially successful in because of their tendency to decompose or otherwise lose their bacteriostatic or microbicidal activity at the high temperatures. Furthermore, scouring and dyeing of the fabrics caused them to lose their antibacterial properties. In addition, many bacteriostats and bactericides are toxic or produce irritant effects and cannot befused in applica- 3,345,341 Patented Oct. 3, 1967 ICC tions in which the polymer article comes in contact with human skin.

It has also been known to incorporate certain bacteriostatic compounds into plastics prior to molding or extruding, or even in the manufacture of coarse, stiff bristles. However, in such products where the surface area is small compared to the volume, the problems of retaining the bacteriostat in the product are minimal for two reasons. First, the surface area varies directly with the diameter, whereas the volume varies directly with the square of the diameter. Second, plastics are extruded at considerably lower temperatures than are fine filaments. The highest denier commercial yarns on the market have diameters of only a small fraction of that of the lowest known bristle diameters. Therefore, the surface area versus volume of yarns is out of all order of magnitude compared to the surface area versus volume of bristles. As a matter of fact, the highest filament denier given in the examples is 15, which is the equivalent of a diameter of 0.015 mm., only about one-tenth of that of the smallest known bristles. 1n the case of such a fine filament, the problems of getting durable antibacterial retention .are most diflicult and many agents that might be retained in plastics will be completely removed either by heat or intensive aftertreatments. It is known that the b-acteriostat in the filament migrates to the surface during aftertreatments and unless it is extremely resistant it will all soon be removed due to the minute volume (diameter of the filament).

It is therefore an object of this invention to produce synthetic high polymer yarn possessing antibacterial activity without the disadvantages normally inherent in the manufacture of yarns having a large surface area as compared to its volume.

Another object of this invention is to provide a novel group of antibacterial agents that may be incorporated directly into a thermoplastic polymer melt and that are able to withstand the melt temperatures of the polymer without degradation or loss of bacteriostatic or bactericidal activity.

Still another object of this invention is to provide thermoplastic polymer yarns possessing antibacterial activity that will retain such activity during processing of the yarns and after subsequent repeated washings.

A further object is to provide synthetic fibers and fabrics having antibacterial activity that can withstand scouring, dyeing, or other phases of fiber and fabric processing and repeated laundering and dry cleaning without substantial loss of their bactericidal and bacteriostatic properties.

A still further object is to provide synthetic fibers and fabrics that will resist the formation of obnoxious odors after contamination with perspiration and prevent the spread of microbiological contamination in garments made from the fibers and fabrics, and on the wearer or wearers thereof.

It is also an object of this invention to provide antibacterial fibers and fabrics which are nontoxic and will not produce irritant effects when placed in contact with human skin.

These and other objects will become apparent from the following detailed description.

In accordance with this invention, antibacterial thermoplastic polymer yarns are prepared utilizing a novel group of antibacterial agents which, when incorporated into a synthetic polymer melt in relatively small amounts, do not decompose or otherwise lose their antibacterial activity at extrusion temperatures; and, in addition, subsequent processing of the yarn as by scouring, dyeing, laundering, etc., does not affect the antibacterial agents sufficiently to cause a substantial diminution in their activity. The compounds that exhibit such antibacterial properties are a very critical and specific group of metal salts of pentachlorophenate and certain pentachlorophenyl esters. These compounds are as follows:

Of the foregoing compounds, lithium pentachlorophenate is the preferable commercial material because it does not noticeably discolor the yarn. If discoloration is not a problem in the end use, others such as cadmium pentachlorophenate may be used.

It has been found that when relatively small concentrations of the aforementioned compounds are incorporated into a synthetic polymer with suflicient mixing to provide a homogeneous composition, a polymer yarn may be produced therefrom having a substantial germicidal activity. Thus, concentrations as low as 0.5% by weight of the antibacterial agent based on the weight of the polymer are sufficient to produce the desired antibacterial activity in the yarn. Preferred concentrations are from 0.5% 1.5% by weight based on the weight of the polymer. While there is no upper limit to the concentrations that may be employed, it has been found that amounts above 1.5% cause discoloration of the polymer and in certain cases adversely affect the strength, elongation, hand, and luster of fiber and fabric products. Thus, care should be taken to see that the concentration does not exceed this limit.

It is preferable to incorporate the antibacterial agents into synthetic high polymers that can be spun or extruded at temperatures below 280 C. because at higher temperatures the agents tend to degrade or decompose. Examples of polymers that are spun at temperatures below 280 C. are nylon 6 (polyepsilon caprolactam) and polyurethanes.

In corporation of the antibacterial agents in the syn thetic polymer may be carried out in various ways. In one method the two materials may be combined simply by adding particles of the antibacterial agent to flakes or chips of the thermoplastic polymer and thereafter thoroughly tumbling the two together to obtain a uniform mixture. Thereafter, a homogeneous dispersion of the antibacterial agent in the polymer is produced when the polymer flake is melted prior to extrusion. Alternately, the two materials may be combined simply by adding the antibacterial agent to the polymer melt with suflicient agitation to effect complete mixing. Obviously, there are other ways to produce a substantially uniform dispersion of the antibacterial agent in the polymer melt and yarn.

The expression antibacterial agent as used herein is intended to mean that such agents have the capacity to either kill or inhibit the growth of bacteria, fungi, molds, and other microorganisms. The antibacterial agents disclosed have general activity against both gram-positive and gram-negative bacteria, although they are particularly active as against the gram-positive variety. The terms gram-positive and gram-negative refer to Grams method for segregating microorganisms based on fundamental biological differences between the two types of bacteria. In general, the procedure consists of staining a fixed bacteria smear with gentian violet solution containing a small quantity of aniline, washing this off with water, and flooding with Lugols iodine solution. The iodine solution is washed off after a time and the smear decolorized with alcohol, acetone, acetone and ether, or some other agent and counterstained with a dye of contrasting color, such as saframine O or Bismarck brown. By this means, bacteria may be divided into two groups. Those which retain the original gentian violet in spite of the decolorization and appear dark purple on a background of the counterstain are spoken of as gram-positive bacteria, and those which are decolorized and are colored by the counterstain are referred to as gram-negative bacteria. Illustrative of specific microorganisms either killed or inhibited by the antibacterial synthetic polymer products of this invention but by no wise limited thereto are:

Micrococcas pyogenes var. aureus (gram-positive) Bacillus subtilis (gram-positive) Proteus valgaris (gram-negative) Escherichia coli gram-negative) Aspergillus niger (mold) Trichophyton mentagrophytes (fungus) Candida albicans (mold) The antibacterial properties of fabrics and yarns produced from synthetic polymers in accordance with this invention are determined by using the prescribed Agar Plate method, a detailed description of which is set forth in the Journal of the American Association of Textile Chemists & Colorists, volume 36, 1960, pages 75-77. In essence, this method comprises seeding a bacteriostasis agar with a test organism such as Micr coccus pyogenes var. aureus. The inoculated agar is then poured into a sterile Petri plate and allowed to harden. A circular swatch of fabric to be tested is pressed gently into intimate contact with the surface of the seeded agar and incubated for a period of 24 hours. The zone of inhibition (halo) in which there is no growth of bacteria is reported in millimeters and is determined simply by measuring the diameter of inhibition and subtracting therefrom the diameter of the fabric sample being tested. Any zone of inhibition is satisfactory, although zones of approximately two millimeters are preferred and considered excellent.

For a more complete and thorough understanding of the invention, the following examples are given to illustrate the method of preparation of the synthetic polymer yarns and the results achieved. However, the invention is not intended to be limited thereby.

Example I Chips of nylon 6 polymer were combined by tumble mixing with 1.5 by weight of lithium pentachlorophenate. This mixture was melted to produce a polymer melt containing approximately 1% by weight of the lithium pentachlorophenate, the loss in antibacterial agent being caused by small amounts clinging to the walls of the mixer and through dusting into the air. The melt thus produced was spun by conventional procedures at 275 C. into yarns having the following deniers and filament counts respectively: 15/1, 210/34, 70/32, and 40/13. These yarns, containing approximately 1% by weight of the phenolic salt substantially uniformly distributed therein, were knit into ladies hosiery or woven or knit into other fabrics in the usual manner and given conventional textile processing treatments (scouring and dyeing). Circular test samples approximately 3 millimeters in diameter were then cut from the hose and fabrics and tested for their antibacterial properties by the Agar Plate method using Micrococcus pyogenes var. aureus as the test organism. The initial zone of inhibition for each sample tested measured approximately 1 to 2 millimeters. After several washings, the zones of inhibition in each case diminished somewhat. However, even after launderings, the fabric samples showed good antibacterial activity. The ladies dyed hosiery was found to withstand more than twenty hand launderings and still have good antibacterial activity and the fabrics produced from the multifilament yarns showed considerable activity even after 25 scourings and up to three hours at the boil. Control fabric samples of conventional nylon 6 containing no antibacterial agent produced no zones of inhibition. Fabric samples were also tested in which the fibers contained from 0.5% to 1.5

f the antibacterial agent. In all cases, the test samples showed good activity.

Example II Swatches of nylon 6 fabric were prepared and tested by the Agar Plate method in the same manner as those disclosed in Example I, except cadmium pentachlorophenate was used as the antibacterial agent. All possessed good antibacterial activity and were able to withstand repeated launderings without substantial diminution in their zones of inhibition. Samples containing as low as 0.5% of the antibacterial agent showed similar activity.

Example III A number of nylon 6 fabric samples were prepared as described in Example I except the antibacterial agent incorporated in the polymer melt was aluminum pentaehlorophenate. All of the fabric samples were tested by the Agar Plate method and all showed excellent antibacterial activity.

Example V A number of nylon 6 fabric sampdes were prepared and tested as described in Example I except the antibacterial agent used was stannous pentachlorophenate. All including the scoured and dyed samples showed excellent antibacterial activity even after repeated laundering operations.

Example VI Two groups of nylon 6 fabric swatches were made from yarns prepared as described in Example I except that the antibacterial agent used in one group was pentachlorophenyl phosphate and in the other group was pentachlorophenyl benzoate. The fabric samples of each group were tested for antibacterial activity by the Agar Plate method and all showed excellent zones of inhibition.

Example VII Several representative fabric swatches prepared as described in each of the Examples I through VI were tested for their antibacetrial activity against the following microorganisms:

Example VIII Nylon 6 polymer containing 1% 'by weight lithium pentachlorophenate was conventionally spun into 1090 denier, 83 filament carpet yarn. The yarn was thereafter 6 tufted into a carpet and processed conventionally by scouring and dyeing. Sample carpet tufts measuring about 5.00 millimeters in length were tested for antibacterial activity using Micrococcus pyogenes var. aureus as the test organism. The samples showed excellent activity. Similar carpet samples tufted from yarns containing the zinc or a cadmium pentachlorophenate were likewise tested and showed similar good activity.

As the foregoing examples clearly show, the synthetic polymer products produced in accordance with this invention have excellent antibacterial properties under a wide variety of conditions and treatments. Moreover, all are nontoxic and do not produce irritant effects when used in contact with human skin. The fabrics retain their activity for prolonged periods of time and still show satisfactory activity after normal textile processing and laundering operations.

Although the invention has been described in detail with reference to particular synthetic yarn products, it is intended that the invention be limited only to the extent set forth in the following claims.

What is claimed is:

;1. A polycaprolactam yarn or filament containing throughout the body thereof 0.5 %1.5 by weight of the polymer from which the yarn is formed, of an antibacterial agent of the group consisting of aluminum pentachlorophenate, zinc pentachlorophenate, tin pentachlorophenate, lithium pentachlorophenate, cadmium pentachlorophenate, pentachlorophenyl phosphate, and pentachlorophenyl benzoate, whereby the yarn or filament will retain its antibacterial activity after it has been subjected to repeated wet processing treatments.

2. The yarn or filament of claim 1 wherein the antibacterial agent is aluminum pentachlorophenate.

3. The yarn or filament of claim 1 wherein the antibacterial agent is zinc pentachlorophenate.

4. The yarn or filament of claim 1 wherein the antibacterial agent is tin pentachlorophenate.

5. The yarn or filament of claim 1 wherein the antibacterial agent is lithium pentachlorophenate.

6. The yarn or filament of claim 1 wherein the antibacterial agent is cadmium pentachlorophenate.

7. The yarn or filament of claim 1 wherein the antibacterial agent is pentachlorophenyl phosphate.

8. The yarn or filament of claim 1 wherein the antibacterial agent is pentachlorophenyl benzoate..

9. A textile yarn product possessing antibacterial properties prepared from a polycaprolactam and melt spun at a temperature below 280 C. having uniformly dispersed therein 0.5%-1.5%, by weight based on the weight of the polymer, of lithium pentachlorophenate.

References Cited UNITED STATES PATENTS 2,216,835 10/ 1940 Carothers 26078 2,507,299 5/ 1950 DAlelio et al. 26078 3,161,622 12/1964 Harrington et a1. 26078 3,200,035 8/ 1965 Martin et a1. 26078 H. D. ANDERSON, Alrsistam Examiner. 

1. A POLYCAPROLACTAM YARN OR FILAMENT CONTAINING THROUGHOUT THE BODY THEREOF 0.5%-1.5%, BY WEIGHT OF THE POLYMER FROM WHICH THE YARN IS FORMED, OF AN ANTIBACTERIAL AGENT OF THE GROUP CONSISTING OF ALUMINUM PENTACHLOROPHENATE, ZINC PENTACHLOROPHENATE, TIN PENTACHLOROPHENATE, LITHIUM PENTACHLOROPHENATE, CADMIUM PENTACHLOROPHENATE, PENTACHLOROPHENYL PHOSPHATE, AND PENTACHLOROPHENYL BENZOATE, WHEREBY THE YARN OR FILAMENT WILL RETAIN ITS ANTIBACTERIAL ACTIVITY AFTER IT HAS BEEN SUBJECTED TO REPEATED WET PROCESSING TREATMENTS. 